FB

LM25085A

PGATE

ISEN

GND

VCC

ADJ

4.5V to 42V

Input

GND

SHUTDOWN

Q1

D1

L1

Cff

GND

VIN

RT

LM25085A

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SNVS601B – JANUARY 2009 – REVISED MARCH 2013

LM25085A 42V Constant On-Time PFET Buck Switching Controller with 0.9V Reference

Check for Samples: LM25085A

1

FEATURES

DESCRIPTION

The LM25085A is a functional variant of the LM25085

2

•

Wide 4.5V to 42V Input Voltage Range

COT PFET Buck Switching Controller. The functional

•

differences of the LM25085A are: The feedback

Current Sense Resistor

reference voltage is 0.9V, the forced off-time after

•

Programmable Switching Frequency to 1MHz

current limit detection is longer, and the soft-start time

is shorter (1.8 ms).

•

No Loop Compensation Required

The LM25085A is a high efficiency PFET switching

•

Ultra-Fast Transient Response

regulator controller that can be used to quickly and

•

Nearly Constant Operating Frequency with

easily develop a small, efficient buck regulator for a

Line and Load Variations

wide

range

of

applications.

This

high

voltage

•

Adjustable Output Voltage from 0.9V

controller contains a PFET gate driver and a high

voltage bias regulator which operates over a wide

•

Precision ±2% Feedback Reference

4.5V to 42V input range. The constant on-time

•

Capable of 100% Duty Cycle Operation

regulation principle requires no loop compensation,

•

Internal Soft-Start Timer

simplifies circuit implementation, and results in ultra-

•

Integrated High Voltage Bias Regulator

fast load transient response. The operating frequency

remains nearly constant with line and load variations

•

Thermal Shutdown

due to the inverse relationship between the input

voltage and the on-time. The PFET architecture

PACKAGE

allows 100% duty cycle operation for a low dropout

•

HVSSOP-PowerPAD-8

sense resistor can be used to sense current for over-

•

VSSOP-8

current detection.

•

WSON-8 (3 mm x 3 mm)

Typical Application, Basic Step Down Controller

1

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2

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PRODUCTION DATA information is current as of publication date.

Copyright © 2009–2013, Texas Instruments Incorporated

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.